This invention relates broadly to fire fighting compositions and methods of applying them. More particularly the present invention relates to a fire fighting solution of improved characteristics in extinguishing fires and permitting greater versatility in the use of conventional fire fighting equipment.
It is not commonly known that fires encountered in the public or private areas throughout the world have been increasingly difficult to extinguish particularly in the last several decades as compared to those fires encountered earlier. It has been found for instance that the material contents of inhabited areas now in existence are often of a very different chemical content or origin than those used previously. In particular, it is the use of synthetic materials which has been increasing of late at the expense of natural materials that has posed a serious problem for the professional fire fighter and public administrators.
New materials used either for construction or decoration have often been found to burn with a hotter flame making fire fighting difficult at best and often times impossible either to salvage precious lives or property. These hotter and more ravaging conditions pose an even greater threat to life due to the prospect of noxious and lethal fumes given off by many of the materials commonly found in these inhabited areas. The combination of the hotter fires and the lethal fumes poses greater problems to combat resulting in fires of greater duration that are often much more than even the most highly skilled and far better trained fire fighter of today is able to cope with for protection of life and property. The time elapsed before extinguishment is particularly important not only to prevent further damage but to stop the evolution of the lethal fumes that are hazards both to the inhabitants and to the fire fighter. Quick and effective fire extinguishment is the only solution.
An ideal fire fighting system will comprise a fire fighting liquid that extinguishes a fire quickly and in particular, cool the fire so that the high heat generated is rapidly reduced. Conventional compositions that may contain various surfactants have not been able satisfactorily to extinguish the fire in acceptable time nor to cool down the fire sufficiently to limit the lethal fumes. Adell, U.S. Pat. No. 3,912,647, for instance, discloses fire fighting compositions containing high concentrations or surfactants blended into a solvent and mixed with water to a viscous substance that is produced in an attempt to blanket the fire. A solvent such as naptha must be used to make the viscous gel flowable. Such high concentrations, in the range of about 3% or more surfactant do not satisfy current fire fighting requirements.
Fire fighting systems and equipment currently available unfortunately have also not matched the rise either in the risk of tragic losses through raging fires or the risks required of the fire fighter. A few new foam making compositions and mechanical systems have been made available in recent years to attack fires but again fire fighting capabilities have not been improved significantly. For instance, fire fighting agents commonly known as aqueous film forming foams (AFFF) are currently in use for application to Class A or Class B fires. However these foams and any other foams have particular drawbacks relating to the rapidity of fire extinguishment and to the means of application when using conventional pumping and discharge equipment.
It is typical of the foam making concentrations that a particular concentrate containing a foam making material such as the fluorinated surfactants are educted into one of a plurality of discharge lines from the commonly used centrifugal pump mounted on the fire truck. The metering means for supplying the desired concentration of the foam making concentrate educted from a supply tank into the discharge line must be sufficiently accurate to provide the desired concentration of the foam making composition. For each of the discharge lines a similar metering and eduction system must be present. These additional metering and eduction systems add substantially to the cost of the fire fighting system and use up valuable space on the fire truck. More importantly, such systems diminish the pump pressure and pump capacity on the fire fighting fluid being discharged thus limiting the distance to which the fire fighting fluid may be dispensed.
Other fire extinguishing foam compositions are known that utilize various nonionic surfactants as additives to aid emulsification and reduce costs when combined with fluorinated surfactants, solvents and foam stabilizing agents. Francen, U.S. Pat. No. 3,772,195, Falk, U.S. Pat. No. 4,090,967 disclose examples of such compositions producing low expansion foams. Typically these formulations are applied through nozzles proportioning 1%, 3% and 6% amounts of the foaming concentrate into the water stream. The nonionic surfactants disclosed in these patents are useful only when combined with fluorinated surfactants because they do not have sufficient wetting ability alone to wet the surfaces of burning organic liquids.
Other U.S. patents such as Dingman, U.S. Pat. No. 3,541,010 and Nieneker, et al., U.S. Pat. No. 3,578,590 disclose additional foam compositions formed from mixtures of ethoxylated alkylphenols and solvents to extinguish fires arising from Class A and B materials. The composition is formed from a concentrate containing a maximum of 30% water necessitating the presence of a solvent to prevent the nonionic ethoxylated alkylphenol from gelling. The concentrate disclosed in the patents produces a foam in which about 0.5 to about 6% by volume of the product exists in the discharged stream.
In every instance such foam formulas are applied into the water stream on only the discharge side of the pump. If the foam formulas are not applied to the water stream on the discharge side of the pump but rather at the intake side excessive foam results causing cavitation of the pump and a total loss of output. Thus each foam discharge line must have its own metering and eductor apparatus which for practical purposes limits the use of only one such foam discharge line on the fire truck for each pump. Typically the requirement of a separate proportioning eductor and foam concentrate supply for each discharge line from the pump is too expensive and requires additional space that is not available. The use of only a single foam line severely limits the effectiveness of the fire fighting apparatus because other discharge lines spraying water would wash away foam sprayed from the single discharge line or else only the single foam line would be used reducing the capability of the fire fighter in extinguishing the fire in the shortest period of time.
Another factor that must be considered as being important to achieve an ideal fire fighting system is the volume of fire fighting solution used to extinguish the fire. This volume may be a critical factor in remote locations where access to water is limited to a portable supply tank accompanying the fire pumper truck. Use of lower volume also is of significant importance in avoiding the extensive water damage commonly experienced by property owners following conventional attempts to extinguish the fire. Fire insurance rates reflect to some extent the fact that in some instances water damage is more detrimental to property than the fire.